[PATCH 5.10 082/406] bpftool: Use a local bpf_perf_event_value to fix accessing its fields

Greg Kroah-Hartman
2023-09-17T19:24:42Z

From: Alexander Lobakin <alobakin@pm.me>

[ Upstream commit 658ac06801315b739774a15796ff06913ef5cad5 ]

Fix the following error when building bpftool:

CLANG profiler.bpf.o
CLANG pid_iter.bpf.o
skeleton/profiler.bpf.c:18:21: error: invalid application of 'sizeof' to an incomplete type 'struct bpf_perf_event_value'
__uint(value_size, sizeof(struct bpf_perf_event_value));
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:13:39: note: expanded from macro '__uint'
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helper_defs.h:7:8: note: forward declaration of 'struct bpf_perf_event_value'
struct bpf_perf_event_value;
^

struct bpf_perf_event_value is being used in the kernel only when
CONFIG_BPF_EVENTS is enabled, so it misses a BTF entry then.
Define struct bpf_perf_event_value___local with the
`preserve_access_index` attribute inside the pid_iter BPF prog to
allow compiling on any configs. It is a full mirror of a UAPI
structure, so is compatible both with and w/o CO-RE.
bpf_perf_event_read_value() requires a pointer of the original type,
so a cast is needed.

Fixes: 47c09d6a9f67 ("bpftool: Introduce "prog profile" command")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230707095425.168126-5-quentin@isovalent.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/bpf/bpftool/skeleton/profiler.bpf.c | 27 ++++++++++++++---------
1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/tools/bpf/bpftool/skeleton/profiler.bpf.c b/tools/bpf/bpftool/skeleton/profiler.bpf.c
index ce5b65e07ab10..2f80edc682f11 100644
--- a/tools/bpf/bpftool/skeleton/profiler.bpf.c
+++ b/tools/bpf/bpftool/skeleton/profiler.bpf.c
@@ -4,6 +4,12 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>

+struct bpf_perf_event_value___local {
+ __u64 counter;
+ __u64 enabled;
+ __u64 running;
+} __attribute__((preserve_access_index));
+
/* map of perf event fds, num_cpu * num_metric entries */
struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
@@ -15,14 +21,14 @@ struct {
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(u32));
- __uint(value_size, sizeof(struct bpf_perf_event_value));
+ __uint(value_size, sizeof(struct bpf_perf_event_value___local));
} fentry_readings SEC(".maps");

/* accumulated readings */
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(u32));
- __uint(value_size, sizeof(struct bpf_perf_event_value));
+ __uint(value_size, sizeof(struct bpf_perf_event_value___local));
} accum_readings SEC(".maps");

/* sample counts, one per cpu */
@@ -39,7 +45,7 @@ const volatile __u32 num_metric = 1;
SEC("fentry/XXX")
int BPF_PROG(fentry_XXX)
{
- struct bpf_perf_event_value *ptrs[MAX_NUM_MATRICS];
+ struct bpf_perf_event_value___local *ptrs[MAX_NUM_MATRICS];
u32 key = bpf_get_smp_processor_id();
u32 i;

@@ -53,10 +59,10 @@ int BPF_PROG(fentry_XXX)
}

for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
- struct bpf_perf_event_value reading;
+ struct bpf_perf_event_value___local reading;
int err;

- err = bpf_perf_event_read_value(&events, key, &reading,
+ err = bpf_perf_event_read_value(&events, key, (void *)&reading,
sizeof(reading));
if (err)
return 0;
@@ -68,14 +74,14 @@ int BPF_PROG(fentry_XXX)
}

static inline void
-fexit_update_maps(u32 id, struct bpf_perf_event_value *after)
+fexit_update_maps(u32 id, struct bpf_perf_event_value___local *after)
{
- struct bpf_perf_event_value *before, diff;
+ struct bpf_perf_event_value___local *before, diff;

before = bpf_map_lookup_elem(&fentry_readings, &id);
/* only account samples with a valid fentry_reading */
if (before && before->counter) {
- struct bpf_perf_event_value *accum;
+ struct bpf_perf_event_value___local *accum;

diff.counter = after->counter - before->counter;
diff.enabled = after->enabled - before->enabled;
@@ -93,7 +99,7 @@ fexit_update_maps(u32 id, struct bpf_perf_event_value *after)
SEC("fexit/XXX")
int BPF_PROG(fexit_XXX)
{
- struct bpf_perf_event_value readings[MAX_NUM_MATRICS];
+ struct bpf_perf_event_value___local readings[MAX_NUM_MATRICS];
u32 cpu = bpf_get_smp_processor_id();
u32 i, zero = 0;
int err;
@@ -102,7 +108,8 @@ int BPF_PROG(fexit_XXX)
/* read all events before updating the maps, to reduce error */
for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
err = bpf_perf_event_read_value(&events, cpu + i * num_cpu,
- readings + i, sizeof(*readings));
+ (void *)(readings + i),
+ sizeof(*readings));
if (err)
return 0;
}
--
2.40.1